The invention relates generally to fiber optic cable distribution enclosures and, in particular, a device providing bend radius control of fiber optic cable entering and exiting said enclosures.
Fiber optical cable allows for high data transmission rates over long distances but its usage is limited by a minimum bend radius. It is desirable to control the radius of the fiber optic cable to prevent the fiber from being bent beyond the minimum bend radius. In addition, it is desirable to eliminate microbending, which occurs, for example, when a fiber optical cable is pulled over a sharp corner. Microbending results in unacceptable high attenuation of the optical signal and degrade or interrupt signal transmission.
Fiber optic cable that is brought into a building for use in transmitting coded or modulated signals, such as telephone (voice), cable (video), or computers (data) signals, must be distributed throughout the building to each location that requires access to the information being transmitted. To facilitate that distribution, an enclosure is typically utilized to house and manage the dispersal of the fiber. FIG. 1 shows an example of such a distribution enclosure 10, which is described fully in U.S. Pat. No. 5,945,633, and is incorporated herein by reference. Distribution enclosure 10 allows cables to enter and exit the enclosure at openings 12. In many cases, as many as 72 fibers are distributed within a single enclosure and several of these enclosures are attached to a rack. In larger systems, a room full of these racks serves as a central hub from which thousands of fibers are distributed.
The multitude of fibers entering and exiting distribution enclosures and the proximity of hardware equipment in a fiber optic cable distribution system, such as described above, result in a high incidence of microbending. Any fiber entering or exiting an enclosure can be subject to microbending by being pulled tight across a sharp edge or pinched between two pieces of hard plastic or sheet metal. The improper functioning caused by the microbending of fibers entering or exiting a distribution enclosure degrades the operability of the entire distribution system.
Prior art devices have been used to protect fiber optic cable from sharp surfaces. A rotatable grommet, shown generally at 20 in FIG. 2 and described fully in U.S. Pat. No. 5,806,140, incorporated herein by reference, is designed for opening or closing access to a distribution panel opening 12 through which fiber optic cable travels. The rotatable grommet 20 protects the fiber optic cable from a sharp edge of the enclosure 10 but does not substantially control the bend radius of the fiber optic cable. Although the device of FIG. 2 is well suited for its intended purpose, it is understood that improvements in the control of fiber optic cable bend radius is needed.